Method of producing patterns for cored castings



y 1958 H. A. GREIS ET AL 2,834,077

METHOD OF PRODUCING PATTERNS FOR CORED CASTINGS Filed May 28, 1954nvmyrozes aDJ/em/ A TTOR/VE/s limited rates Patent METHOD OF PRGDUINGPATTERNS FOR CORE!) CASTINGS Howard A. Greis, Cedar Grove, N. 3., andJohn R. Watson, Wauwatosa, Wis.

Application May 28, 1954, Serial No. 433,054

3 Claims. (Cl. 22-194) The invention relates in general to improvementsin the foundry art, and relates more specifically to an improved methodof fabricating patterns and cores for the production of castings havinginternal passages or ducts.

The primary object of the present invention is to provide an improvedmethod of economically producing durable castings having accuratelyformed and smooth internal conduits of diverse shapes, from varioustypes of castable metals and other materials.

In various industries and especially in the manufacture of hydraulic,pneumatic and other fluid conducting manifolds and other cored castings,it is frequently necessary to provide castings each having one or morepassages or spaces of diverse dimensions and shapes, some of which areinterconnected while others are independent. Heretofore, such castingshave been produced either by utilizing the usual patterns and cores toform the final casting molds, or by employing plastic patterns inso-called investment casting methods to provide the required coredspaces in the molds. With prior investment casting methods involving theuse of molded plastic patterns, the patterns were of necessity made inconfigurations that could be readily withdrawn from the pattern mold.These patterns were used to form simultaneously both the internal andexternal casting surfaces, with the result that only short, simplyshaped passages could be formed, except by tedious and costly moldfabrication techniques. However, all of these prior methods offabricating such patterns and castings are expensive and slow while alsoresulting in the production of numerous defective molds and castings.

It is therefore an important object of this invention to provide animproved process of manufacturing cast hydraulic manifolds or the like,by facilitating the construction of the patterns for the fluidconducting passages and insuring the formation of smooth andunobstructed ducts in a rapid and inexpensive manner.

Another important object of the present invention is to provide a methodof fabricating conduit cores of any desired length and configuration formolds utilized to produce castings embodying such cores, and wherein theformation of the cores is effected with the aid of patterns constructedfrom readily available materials.

A further important object of the invention is to provide an improvedmode of producing castings having one or more smooth surfaced ductstherein, from diverse metals or castable material, by utilizing aplastic or other easily removable shell to form a refractory corefor-each of the required ducts and by eliminating these shells beforethe cores are applied to the final mold.

Still another important object of our present invention is to provide asimplified and inexpensive system for producing castings having avariety of internal passages of diverse lengths, cross sections andshapes, with accurately formed core patterns devoidof objectionablecavities or other defects. 7

An additional important object of this invention is to provide variousimprovements in the art of fabricating 2 extremely durable hydraulicmanifold castings or the like, having smooth and unobstructed straight,curved or otherwise formed conduits emanating therefrom and crossingeach other if desired, and which may be expeditiously manufactured toWithstand high, pressures.

These and other more specific objects and advantages of the presentinvention will be apparent from the following detailed description.

A clear conception of the several steps involved in the commercialexploitation of our invention and several modifications thereof, may behad by referring to the drawing accompanying and forming a part of thisspecification wherein like reference characters designate the same orsimilar parts in the various views.

Fig. 1 is a central longitudinal section through a typical compositecore pattern or shell for producing an elongated conduit core havingopposite end elbows and a medial off-set connected with the elbows bystraight tubular portions;

Fig. 2 is a similar section through the pattern or shell of Fig. 1, butshowing the same inverted and initially filled with a mass or coreforming material;

Fig. 3 is another similar section through the core laden pattern orshell of Fig. 2, but with the shell provided with local stress relievingincisions or cuts;

Fig. 4 is an elevation of the molded core produced with the severalsteps depicted in Figs. 1, 2 and 3, but with the pattern shell removed;

Fig. 5 is a perspective view of a pattern or shell somewhat similar tothat illustrated in Fig. l, but which has been split along alongitudinal central plane in order to effect assembly thereof andremoval from the cores for reuse; I

Fig. 6 is a vertical central section taken through a typical'completedmold showing several ditferent types of conduit cores constructed inaccordance with the invention, mounted therein preparatory to theproduction of a casting embodying passages simulating the cores; and IFig. 7 is a transverse vertical section through the mold and coreassemblage of Fig. 6 showing the cores in elevation.

While the invention has been shown and described herein as beingespecially advantageously applicable in the production of cast hydraulicmanifolds having internally smooth passages or ducts communicatingthrough elbows with one or more faces of each manifolchit is not theintent to unnecessarily restrict the improved production method to suchfield or industry; and it is also contemplated that specific descriptiveterms employed herein be given the broadest possible interpretationconsistent with the disclosure.

In accordance with this invention and as illustrated in the drawing,each individual conduit pattern or shell may consist of a single tube orit may be built up from one or more extruded or cast internally smoothtube sections 8, 9 of the desired internal cross section and cut tospecific lengths and having elbows or fittings 1t), 11 of any suitableconfiguration secured to the outer ends of the tube sections 8, 9 so asto provide smooth internal joints at the adjoining ends of the tubes andfittings as illustrated in Fig. 1. The inner or adjacent ends of thetube sections 8, 9 may be likewise interconnected by another fitting 12of like internal cross section, to provide an off-set in the pattern,but the tubular shell may if desired, be produced from a single tubularsection connected to the end fittings 1t 11 and the requisite offsetsmay be produced by locally bending this single continuous section. Inany event, the interior of each pattern must substantially conform withthe external dimensions of the core which is to be produced, and shouldhave a smooth internal surface devoid of objectionable interruptions,cavities or projections.

When constructing these .core patterns or shells it is preferable toutilize extruded plastic tubing and cast or extruded fittings formed ofeither plastic, wax, or any other suitable material, which is relativelysolid and rigid under normal conditions, :and can, preferably, bereadily formed, molded or extruded, but which may be split into parts ordisbursed either by heating or chemically, or otherwise. The shellforming material preferably should also be sufiiciently transparent sothat the internal surfaces thereof can be inspected and that theintroduction of core forming material may be observed. It is alsopreferable to employ pattern forming substance which may be readily cut,and distorted when subjected to heat, and the several sections 3, 9 andfittings 1.0, 11, 12 may i be united by cementing, weldingor otherwise.

In order to produce a typical pattern or shell such as shown in Fig. 1,it is first necessary to determine the dimensions of the core which itis desired to form, after which plastic tubing of the proper internalcross section should be provided and either secured to the ends of apro-formed fitting 12, or bent to provide the desired offset. Thetubular sections 8, 9 should then be cut to proper length whereupon theend elbows ll), 11, if required, should be applied to the cut outer endsof the sections 8, 9. if the shell is to be expendable during removalfrom the core, the pattern will be complete upon attachment of theelbows; but in cases where it is desired to save the shell for re-use,it may be split longitudinally as in Fig. into two or more parts 14, 15adapted to be clamped together while the core forming material is beinginserted, and to be subsequently separated in order to remove the moldedcore.

With the above described initial step of the present method, eitherdestructible or re-usable patterns may be readily produced fromplastics, waxes, or the like, with the aid of standard tubing andfittings of various internal cross-sections and lengths, and theinteriors of these shells may be formed smooth and of substantially theshape of i the desired cores. It is important to note that the interiorsof these patterns or shells determine the final shapes of the coreswhile the exteriors thereof have no effect on these cores, and that awide variety of patterns or shells may be produced without utilizingspecial and costly dies.

After each pattern has been thus produced, the next step is to fill thesame with refractory core forming material 17. This material may beeither a liquid slurry of refractory substance adapted to set bychemical action or hydration, or a semi-fluent relatively dry refractorysubstance likewise adapted to set or held sufficiently firm by bondingagents within the refractory, and in either case introduction of thematerial may be facilitated by inverting the shell as in Fig. 2. Anyrefractory core forming material which is of sufiicient strength toretain its shape during pattern removal and core baking, may beutilized, and in either case the pattern must be completely filled withmaterial 17 so that no voids or air pockets remain on the core surface.By utilizing transparent material in forming the shells, loading of thelatter with refractory material 1'7 is also facilitated especially whenproducing cores of relatively small crosssection and of great length andhaving several medial bends therein. Examples of refractory materials 17which may be used, are gypsum, other plaster compounds, or clay forproducing aluminum or bronze castings, and substances such as ethylsilicates when producing other metal castings; and the properpositioning of the cores within the molds during casting is alsoimportant as will be later explained.

When split patterns or shells such as shown in Fig. 5 are utilized, thecores 1'? when set may be readilyremoved by merely releasing the clampsfrom the parts 14,

15 and byseparatin'g these parts.- However, in cases where the number ofsimilar cores 17 required does not warrant the provision of split shellsor patterns, these shells may be removed by burning, cutting, stripping,or chemical action. In cases where the patterns are to be thus expendedor destroyed when being removed from the cores 17, provision mayberequired to prevent possible distortion or destruction of the coresduring removal, especially when removed by heating. The removal of thepatterns by heating or burning is also preferable since it combinesdrying of the cores 17 with the removal while the shells are beingmelted or burned off, but in order to permit the plastic patterns toshrink without detrientally affecting the confined cores 17 it ispreferable to provide a series of local stress relief incisions or cuts19 as illustrated in Fig. 3. The pattern and core assemblages may thenbe heated to elevated temperatures whereupon the plastic shells will bemelted or burned off and the finished and relativelydry cores 17 shownin Fig. 4 will result.

Before the set cores 17 are finally applied to a mold 20 as in Figs. 6and 7, they should be baked in an oven so as to insure completedehydration and also to complete any chemical action which might takeplace in the core forming material. tached to a base section 21 of themold 20, the sides and bottom of which determine the size and shape ofthe casting desired and which has an upper opening 22 which serves as ariser for the casting. The cores 17 should also be positioned as shown,with the elongated medial portions thereof inclined relative to thefluid level of the molten metal, in order to facilitate the escape ofgases and to avoid gas confining pockets, and when the cores have beenproperly positioned the entire mold assembly should be heated before thefinal pouring operation takes place. The final casting may thereafter beeffected with the pressure of the admitted casting material sufiicientlyhigh to force entrapped gases from the mold 2i) and to obtain intimatecontact of this metal with the smooth surfaces of the cores 17, and thetemperatures of the metal should also be properly controlled in accordwith normal foundry procedure.

It has been found that by following the. foregoing steps, intricatecastings of metal and other castable materials and having exceptionallysmooth and accurately formed cored internal surfaces may be economicallyproduced with minimum effort and great dependability. When re-usablesplit patterns comprising separable parts 14, 15 are utilized, theseparts should be formed more durable and somewhat thicker than whenexpendable shells are employed, but the important feature of theimproved method is the formation of smooth surfaced patterns and coresfor producing internal smooth and accurately shaped cored surfaces onthe final castings. The patterns or shells are utilized only to producethe cores and not the castings, and need not be introduced within themolds, but it is also important when assembling cores within the moldsto make proper provision for avoiding entrapment of gases. Whenemploying patterns which are removed by heating, it is also important toprevent distortion or destruction of the cores 17 due to shrinkage ofthe shells during pattern removal, and the improved method has provenhighly satisfactory and successful in actual use. It is also noteworthythat the present improved method makes it possible to produce molds withcomposite patterns some parts of which are formed of plastic while otherparts are formed of different materials ordinarily utilized in patternconstruction. This procedure enables the more intricate parts of thepatterns to be readily produced at low cost of the plastic material,while other more simple parts may be likewise produced by ordinarypattern making methods.

It should be understood that it is not desired to limit this inventionto the exact steps of the method herein shown and specificallydescribed, for various modifica- The cores 17 may then be at tionswithin the scope -of the appended claims may occur to persons skilled inthe art.

We claim:

1. The method of producing a mold for casting a unitary flat manifoldhaving therein several segregated and crossing fluid conducting conduitsterminating at a flat side of the final casting, which comprises,endwise uniting straight and arcuate end and medial sections of tubingformed of plastic having uniform Wall thickness and smooth interiors toprovide an independent pattern for each conduit having the sameconfiguration and dimensions as those of the required final conduit,completely filling each tubular pattern with self-hardening refractorycore forming material and after said material has hardened removing theplastic pattern from each hardened core having curved ends formed bysaid arcuate tube end sections, die molding a fiat manifold cavitycorresponding to the external shape of the final casting desired, andmounting the arcuate core ends at one side of the mold cavity to supportthe intermediate core portions within the cavity with arcuate medialportions thereof crossing but spaced from adjacent medial portions ofother cores.

2. The method of producing a mold for casting a unitary flat manifoldhaving therein several segregated and crossing fluid conducting conduitsterminating at a flat side of the final casting, which comprises,endwise uniting straight plastic tubing sections with arcuate end andmedial sections of similar tubing all having uniform wall thickness andsmooth interiors to provide an independent pattern for each conduithaving the same internal configuration and dimensions as those of therequired final conduit, completely filling each tubular pattern withself-hardening refractory core forming material and after said materialhas hardened removing the plastic pattern from each hardened core havingelbow ends formed by said arcuate tube end sections, molding a cavitycorresponding to the external shape of the final casting desired andbounded on one side by a fiat base board, and mounting the core elbowends to position the intermediate core portions within the cavity witharcuate medial portions thereof crossing but spaced from adjacent medialportions of other cores.

3. The method of producing a mold for casting a unitary fiat manifoldhaving therein several segregated and crossing fluid conducting conduitsterminating at a flat side of the final casting, which comprises,endwise uniting straight and arcuate end and medial sections of heatdisbursable tubing having uniform wall thickness and smooth interiors toprovide an independent pattern for each conduit having the sameconfiguration and dimen-' sions as those of the required final conduit,completely filling each tubular pattern with refractory core formingmaterial and heating the assemblage to harden the confined material,thereafter removing the plastic pattern from each hardened core providedwith elbow ends formed by said arcuate tube end sections, molding acavity corresponding to the external shape of the final manifolddesired, and mounting the core elbow ends at one side of the mold cavityto support the intermediate core portions entirely within the cavitywith arcuate medial portions thereof crossing but spaced from adjacentmedial portions of other cores.

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